Another "What Should I Buy" Thread -- Currently own ATH-M50, looking to upgrade

So i've been using my ATH-M50 for a while now and they're awesome. Great passive sound isolation, good base, overall a fantastic pair of cans.

I've been looking to upgrade to something a bit higher end, the problem is that my main driver will be an iPhone, and I dont wan't to be carrying around a headphone amp, so I feel like that cuts out alot of choices. 

The Bowers & Wilkins have a striking look, and amazing build quality, and from my 5-10 minute session with them at an apple store have pretty good sound. I see conflicting reports about these cans, and don't want to invent ~$300 in a pair of phones that will end up disappointing (I've heard burn in for these is quite long ~300 hours). 

So Head-Fi experts, do you have any other headphones I should be looking at? I listen to lots of different kinds of music, mostly jam bands (Phish etc.), some electronica/techo/psytrance (Pretty Lights, Infected Mushroom), and a lot of other stuff, so a good all-rounder is important to me (thats why I like the ATH-M50). I want these to be full size headphones, but the more portable the better (another reason the P5s intrigue me). Build quality and looks are also somewhat important, it would be nice if the cans looked good as well as sounded good (though sounding good is by far more important). 

Thanks in advanced for all the advice guys :)

thanks for the advice guys, no IEM for me, unfortunately I cant stand them. I also do listen to jam bands more than anything else so getting those crisp highs and mids is important to me, as well as some funky bass. 

portability is pretty key for me. this would be mostly for in office and on the go use (NYC subways, streets, etc.), so sound isolation is pretty important. thanks again!